System for range tracking



Jan. 25, 1966 J. ONIA 8 SYSTEM FOR RANGE TRACKING Filed April 19, 1952 2 Sheets-Sheet 2 E l g i INVENTOR.

JOH/V O/V/A BY MQ-W ATTORNEY United States Patent 3,231,888 SYSTEM- FOR RANGE TRACKING John Onia, Berkley, Mich.,.assignor to The Bendix Corporation, a corporation of Delaware Filed Apr. 19, 1952, Ser.No.- 283,227 12 Claims. (Ci. 343--7.3)

This invention relates to a system for and method of tracking the range of a target and more particularly to a system for and method of accurately tracking a target 50 that a missile can eventuallyintercept and destroy .the targetwithout losing its sight.

In certain types of missiles, the missile antenna is pointed at a target before beinglaunched and is thereafter maintained pointed at the target, even during flight. After being launched, the missile is rapidly accelerated to a great speed far exceeding the speed of the ,target,.which may be moving at a relatively great speed itself. In this --way, the missile is able to quickly overtake and intercept the target, regardless of the flight path which the target may adopt.

To distinguish between the particular target and extraneous objects in the range of the missile antenna, the ;missile has electrical circuits .Which track the target.

These circuits take accountof the distance between the missile and the target. at any inst-ant and the speed at which the missile is approaching the target at that instant. The circuits then allow only. pulses reflected from objects ,in the vicinity of the target to activate equipment for directing the future course of the missile.

One disadvantage of the tracking circuits now in use is 1 that they do not operate satisfactorily during the time that 1 the missile is being accelerated to its maximum speed after being launched. Because of-the considerableacceleration of the missile during the first few seconds after being launched, the tracking circuit in the missile often loses sight of the target and prevents the missile from thereafter effectively overtaking the target. The missile may even start to pursue a friendly object, such as a friendly airplane, if the object is in the vicinity of the target at the instant that th missile loses sight of the target.

This invention provides a range tracking system which maintains the missile locked on the target even during the time that the missile is being considerably accelerated after being launched. The system provides a compensation for the missile acceleration by producing an electrical signal proportional to the missile acceleration. This electrical signal is then combined in a predetermined manner with other signals representing the target position and -velocity relative to the missile at any instant so as to produce a resultant signal Which deter-mines the time at which pulses are to bereceived from the target.

Anobject of this invention is to provide a system for tracking a target so that a missile in which it isused can eventually intercept the target.

.Another object of this invention is to provide a system of the above character for keeping a target in sight even during the time that the missile is being considerably ac- 'celerated to its maximum speed after being launched.

A further object is to provide a system of the above character for producing a signal proportional to the acceleration of a missile and for combining this signal with tector28 connected to a receive'r' 3t). vThe signals intro- 3 131,888 Patented Jan. 25,

other signals to producea resultant signal for trackinga particular target.

Other objects and advantages will be apparent from a detailed description of the invention and from the ap- .pended drawings and claims.

.difierentiator. 14, which isin cascade arrangement with an amplifier 16, an early gate'generator. 18 and a late gate generator 20. i

The output terminals of the generators 18, and 26) are connected to the suppressor gridsof the pentodes in an early gate amplifier Z2. and alate'gate amplifier 24, respectively. The control grids ofthe pentodes in the amplifiers 22 and 24 are connected to the output terminal of amplifiers 26,which have signalsintroduc'ed to them from a deduced to the receiver 30 maybe picked up by the antenna 13. i i i Connections are made from. the plate of the pentode in .the amplifier 24 through a suitable capacitance 32 to the cathode of a diode 34 and from the plate of the pentode inthe amplifierZZ through a suitable capacitance 36 to the cathode of a diode 3:8. The plate of the diodef34 is connected to the cathode of the diode .38 through a resistance 40, to the control grid of a pentode 42 and to a capacitance fl t, which -i-s in series with a grounded capacitance 46. 4

The cathode-and suppressor grid of the tube 42 are connected through a resistance itito the cathode of the diode 34 and through a resistanceto. the plate of a tube 52. The plate of the tube 42 is adapted to receive a direct positive voltage, such as 200 volts, from a power supply 54,

and the screen grid is adapted to receive adirect positive voltage from the power supply through a resistance 56.

In addition to being connected to the resistance 50, the plate of the tube 52 islconnec'ted through a resistance ;58 to the plate of the diode 38, which also has agrounded capacitance 60 connected to it. Connections are made from the grid of the tube 52 to a grounded resistance62 and to a resistance 64 in series with a resistance 66, the

V resistance 66 being connected to the cathode of the tube.

A negative voltage from the power supply 54 is applied to the common terminal between the resistances 64 and 66.

The power supply .54 also applies a positive voltage to the plate of a tube 68. The grid of the tube 68 isbiased at the same voltage as that on the grid of the tube 42, and the cathode of the tube 68 is connected to a grounded resistance70 and through a resistance/72 to the common terminal between the capacitances 44 and 46. The cathode of the tube,68 is also connected tov the grid of the left tube in the multivibrator 12.

The bias on the common terminal between the capacitances 44 and 46 is controlled, at least partially, by the current passing into the capacitance 44 from an amplifier 74, as will be disclosed in detail hereafter. The output terminal from the amplifier 74 is connected through a relatively large resistance 76 to the capacitance 44, and the input terminal is connected to a detector 78. Connections are in turn made from the input terminals of the detector to the right terminals of a pair of linearly disposed windings 80 and 82, the left terminals of which are grounded.

The windings 80 and 82 are magnetically coupled by an armature 84 to a pair of windings 86 and 88 having their inwardly positioned terminals grounded and their outwardly positioned terminals connected to an alternator 90. The armature 84 is attached at one end to a spring 92, which is in turn secured to a wall 94 of a missile (not shown) in which the system disclosed above is housed. The other end of the armature 84 is attached to a suitable mass 96. The armature 84 is so positioned by the spring 92 and the mass 96 that it lies equidistant between the windings 80 and 82 in the axial direction of the windings when the missile has no acceleration.

In the embodiment disclosed above, the trigger source produces pulses at a predetermined and relatively low frequency. Each of these pulses triggers the transmitter 11 and causes the transmitter to radiate signals at a relatively high frequency during the pulse. The high fre quency signals are beamed by the antenna 13 towards a target (not shown) and are reflected by the target back to the transmitter antenna, which passes them into the receiver 30.

At the same time that each pulse from the source 10 triggers the transmitter, it also triggers the normally coniduc-tive left tube in the multivibrator 12 and causes the left tube in the multivibrator to become cut off and the right tube to start conducting. The left tube in the multivibrator 12 remains cut off for a period of time dependent upon the bias on the grid, as will be disclosed in detail hereafter. The positive pulse on the plate of the left multivibrator tube is illustrated at 100 in FIGURE 2.

When the left tube starts to conduct again, it produces a negative pulse of voltage on its plate. This pulse is differentiated by the diiferentiator 14 to produce a negative triggering signal, indicated at 102 in FIGURE 2. After being amplified, the signal 102 is introduced to the early gate generator 18, which produces a pulse 104 having first a positive and then a trailing characteristic. The trailing characteristic of the pulse 104 is differentiated and inverted and is then introduced to the late gate generator 20 for triggering the generator into producing a pulse 106 ductive left tube in the multivibrator 12 and causes the The pulses 104 and 106 from the generators 18 and 20 are mixed in the amplifiers 22 and 24 with the received signals after the received signals have been amplified and detected, the detected signals being indicated at 108 in FIGURE 2 Because of the voltage bias applied to it, each of the amplifiers 22 and 24 passes signals only when a pulse from the detector 28 coincides with a pulse produced by the gate generator associated with the amplifier.

If a received pulse 108 coincides substantially equally in time with a pulse 104 from the generator 18 and a pulse 106 from the generator 20, the amplifiers 22 and 24 pass signals having substantially equal amplitudes and durations. Since these signals have substantially equal strengths, they produce no change in the bias across the diodes 34 and 38 when introduced to the cathodes of the diodes.

It may sometimes happen that the pulse 108 is positioned relative to the pulses 104 and 106 to produce a signal 110 of substantially maximum strength from the amplifier 22 and no signal from the amplifier 24. In such a case, the signal 110 passes through the capacitance 36, the tube 38 and the capacitance 60 and charges the capacitance 36 with a negative charge on its left plate and a positive charge on its right plate.

At the end of the signal 110, the left plate of the capacitance 36 returns to a potential of substantially ground. However, the positive charge accumulated on the right plate causes the voltage on the plate to rise above ground and to raise the voltage on the grid of the tube 42 in a positive direction. The increased voltage on the grid of the tube 42 causes the current through the tube to increase, with a corresponding increase in the voltage across the resistance 48.

As previously disclosed, the tube 42 is in a series circuit which includes the power supply 54, the tube 42, the resistance 50, the tube 52, and the resistance 66. The tube 52 is included in the circuit to serve as a means for maintaining a constant current regardless of any variations in the voltage applied between its plate and cathode. The tube also provides a relatively large impedance in the circuit.

Because of the constant current action and the large impedance provided by the tube 52, the tube 42 has a gain of substantially unity. The gain of substantially unity through the tube 42 causes the voltage on the cathode of the tube to follow the voltage on the grid so that a substantially constant voltage difference appears between the cathode and the grid. This constant voltage difference is also applied across the tube 34 since the tube 34 is connected between the grid and cathode of the tube 42.

Because of the connections between the grids of the tubes 42 and 68, the tube 68 conducts in accordance with any changes in the voltage applied from the capacitance 36 to the grid of the tube 42. Therefore, any increase in voltage on the grid of the tube 42 produces a corresponding increase in the current through the tube 68 and a corresponding increase in the voltage across the resistance 70. This rise in the voltage across the resistance 70 is applied to the grid of the left tube in the multivibrator 12 to decrease the length of time during which the tube is cut off. In this Way, the early and late gate generators produce their pulses 104 and 106, respectively, at an earlier time after the transmission of a pulse towards the target, and the pulse 108 received from the target coincides substantially equally in time with the pulses 104 and 106.

Similarly, a negative pulse is produced by the amplifier 24 when the received pulse 108 occurs at substantially the same time as the pulse 106 from the late gate generator 20. The pulse from the amplifier 24 causes the voltage on the cathode of the tube 34 to decrease. Since the voltage on the plate of the tube 34 tends to follow the voltage on the cathode, a decrease in voltage is produced across the capacitances 44 and 46 and on the grids of the tubes 42 and 68. The decrease in voltage on the grid of the tube 68 causes the current through the tube to decrease, thereby producing a decrease in the voltage across the resistance 70. The resultant decrease in the voltage on the grid of the left tube in the multivibrator 12 causes the tube to be cut off for an increased period of time. This action continues in an ideal system until the received pulse 108 has substantially equal coincidence with the pulses 104 and 106.

An equality of time coincidence between the received pulse 108 and the gate pulses 104 and 106 would certainly exist if the missile and the target remained at a substantially constant distance from each other. Since the missile is overtaking the target, however, it has a relative speed with respect to the target along a line of sight between it and the target. This relative speed causes the received pulse to arrive at an earlier time than anticipated by the range tracking system and to produce an error signal, the magnitude of which is determined by the relative speed between the missile and the target. This error signal causes an adjustment to be made in the times at which the signals from the early and late gate generators are produced in a manner similar to that disclosed above. After an adjustment has been initially made between the missile and the target, no further adjustment is required as long as the relative velocity remains constant. Thus, the system takes account of both the distance between the missile and the target at anyinstant and the relative fjspeed at which-the missile is approaching the target at that instant along the line of sight.

'For an accurate system of range tracking, compensation for the relative speed between the missile and the target is not'enough. This is especially true during the first few seconds after the missile has been launched, during which time the missile may have an acceleration up to 30 g, g being the pull of gravity. Since the target generally "has a maximum acceleration of only approximately6 g, thediffe'rence in the accelerations of the missile and the target can often produce an error which causes the range tracking system to completely lose sight of the target *shortly after the missile is launched. Such loss of sight is produced when each pulse 108 received from the target does not coincide at all with either the gating'pulse 104 or the gating pulse 106. Once the range tracking system loses sight of the target, it may fly'without purpose until it locks on another object, either friend or foe. Thus, the missile may eventually destroy a friendly object, such as a'friendly aircraft.

One Way of making the range tracking circuit more sensitiveto changes in missile velocity might be to increase the amplification of the signals received from the target. This'would be entirely satisfactory except for the corresponding increase in the gain of the noise received from f extraneous causes. Thus, since no material increase would be produced in the 'signal-to-noise ratio by further amplification of the received signal, the sensitivity of the circuit couldnot be increased materially in this manner.

This invention provides components, including alinear differential transformer formed by the armature 84 and the windings'80, 82, 86 and 88, to compensate for the missile acceleration. As previously disclosed, the arma- "ture84 is normally positioned so that half of it'provides a magnetic coupling between the primary windings and thejsecondary winding 80 and the other half provides a couplingfbetween the primary windings and the secondary "winding 82. Thus, for an intermediate position of the armature 84, equal voltages are induced in the windings 80 and 82 by alternating signals from the alternator" 99 applied to the primary windings 86 and'88, and these equal voltages are cancelled in the detector 78 to produce no output signal. 7

When the missile starts to accelerate in the direction of the line of sight between it and the target, its wall94 is provided with a movement relative to the mass 96because 'of the inertia of the mass. This causes the armature 84 to become displaced so that an unequal magnetic coupling is produced between the primary windings and each of the secondary windings 80 and 8-2. For example, the armature maybe shifted to the left from its intermediate posi- "tion between the windings 80 and 82 when the wall 94 is accelerated to the right.

' Upon the shift of the armature 84 from its intermediate position, the voltages induced in the windings 80 and 82 become unequal because of the ditterences in the magnetic couplings to the windings. The difference between the unequal voltages is then'determined by the detector 7 8 and amplified, and the amplified signal is applied through the resistance 76 to the capacitance 44.

The amplifier 74 is included to increase the voltage that is produced, and the resistance 76 is inserted into the circuit to isolate the amplifier from the capacitance '44.

J Since the resistance 76 has a relatively large value, only a relatively small current flows through a circuit including the amplifier 74, the resistance 76 and the capacitances44 and 46. Because of its small value, this current is re-.

changes in load voltages and other extraneous causes.

The current flowing through the resistance 76 charges "the capacitances 44 and 46 and produces on the grids of the tubes 42 and 68 an increase in voltage determined by the increase in charge. This increase in the voltage on the grid ofthe tube 68 produces a corresponding increase in the voltage on the cathode of the tube and on the grid of the left'tube in the multivibrator 12. Because of the increase in grid voltage, the multivibrator' 12 operates to decrease the delay of the times at which the early and late gate pulses are produced by the generators 18 and'20, respectively. In this way, the system disclosed above takes account-of the missile acceleration as well as the. distance between the missile and the target and the relative velocity between them.

It should be realized that other means than a linear differential transformermay be used to produce a signal responsive to missile acceleration. 'For example, a crystal may be retained within the missile: to produce a signal having an amplitude proportional to the pressureexerted on it, the pressure being exerted on the crystal .in accordtrated with reference to particular applications, the principles involved are susceptible of numerous other applications which will be apparent to persons skilledin the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

What is claimed is:

1. In combination in a system for tracking a-target for the interception of the target by a missile, means for producing a pair of gate signals,means for receiving a signal from the target,-means for producing an-error. signal having an amplitude dependent upon the coincidence between each gate signal and the received signal to provide an indication of the distance between the missile and the target and the velocity ofthe missile towards the target,

means-for varying the amplitude of the error signal in accordance with the acceleration of the missile, and means for varying the time at which the gatesignals are produced in accordance with'the amplitude of the error signal.

2. In combination in a system for tracking a target for the interception of the target by a missile, means. for producing first gate signals, means for producing second gate signals immediately afterthe first gate signals, means for receiving signals from the target, means for mixing the received signals with the first gate signals and with thessecond gate signals to produce a pair oferror signals having durations dependent upon the times at which the signals gate signals are produced.

3. In combination in a system for tracking atargetfor the'interception'of the target by amissile, means for producing first gate signals, means. for producing second gate signals immediately. after the first gate signals, means for receiving signals from the-target, a capacitance, means for increasing the charge across the capacitance in accordance with the time of coincidence between the-first gate signals and the received signals, means for decreasing the charge across the capacitance in accordance with the time of coincidence between thesecond gate signals and the received signals, means for varying the charge across the capacitance in accordance with the acceleration of the missile, and means operative in accordance with the charge across the capacitance to vary the times at which the first gate signals and second gate signals are produced.

4. In combination in a system for tracking a target for the interception of the target by a missile, means for producing first gate signals, means for producing second gate signals immediately after the first gate signals, means for producing signals for transmission towards a target, means for receiving signals reflected from the target, a tube, means for increasing the current through the tube in accordance with the time of coincidence between the first gate signals and the received signals and for decreasing the current through the tube in accordance with the time of coincidence between the second gate signals and the received signals, means for increasing the current through the tube in accordance with the acceleration of the missile in the direction of the target, and means operative in accordance with the current through the tube to vary the times at which the first and second gate signals are produced relative to the times at which signals are produced for transmission.

5. In combination in a system for tracking a target for the interception of the target by a missile, means for producing a pair of gate signals, means for receiving pulses reflected from the target, means for mixing the pulses with the gate signals to produce a pair of error signals having strengths determined by the relative coincidence between the received pulses and the gate signals, means operative in accordance with the relative strengths of the error signals to produce a first error signal having an amplitude indicative of the relative velocity between the missile and the target at that instant, means for producing a second error signal indicative of the acceleration of the missile at any instant, means for combining the first and second error signals to produce a resultant error signal, and means for adjusting the time at which the gate signals are produced in accordance with the value of the resultant error signal.

6. In combination in a system for tracking a target for the interception of the target by a missile, means for producing a balanced pair of voltages, means for unbalanc- -ing the voltages at any instant by an amount dependent upon the relative velocities between the missile and the target at that instant, means for producing a signal having an amplitude dependent upon the acceleration of the missile at that instant, means for adjusting the unbalance of the voltages in accordance with the amplitude of the signal, and means operative in accordance with the unbalance of the voltages to provide for the passage of signals received from distant objects at approximately the time that the signals are expected from the target.

7. In combination in a system for tracking a target for the interception of the target by a missile means for producing a balanced pair of voltages, means for unbalancing the voltages at any instant by an amount dependent upon the relative velocity between the missile and the target at that instant, means for adjusting the unbalance in the voltages at any instant by an amount dependent upon the acceleration of the missile at that instant, and means operative in accordance with the unbalance between the voltages to adjust the time at which signals received from distant objects will be passed.

8. In combination in a system for tracking a target for the interception of the target by a missile, a pair of capacitances, means for providing an initial balance of charge between the capacitances in accordance with a first determination 'of the distance between the target and the missile, means for providing an unbalance of the charges on the capacitances in accordance with the relative speed between the missile and the target, means for providing a decrease in the unbalance of the charges on the capacitances in accordance with the missile acceleration, and means operative by the unbalance on the capacitances to produce a gating signal for passing received signals at approximately the time that signals traveling from the target will be received at the missile.

9. In combination in a system for tracking a target for the interception of the target by a missile, a pair of capacitanoes, each capacitance being adapted to receive a balanced charge relative to the charge on other capacitance, means connected to the capacitances to provide an unbalance in the charges on the capacitances at any instant in accordance with the relative velocity between the missile and the target at that instant, means connected to the capacitanees to provide a decrease in the unbalance of the charges on the oapacitances at any instant in ac cordance with the acceleration of the missile along the the line of sight at that instant, and means operative in accordance with the unbalance between the capacitances to produce a coincidence between the time that signals are received from the target and the time that received signals are passed.

10. In combination in a system for tracking a target for the interception of the target by a missile, means for producing first gate signals, means for producing second gate signals immediately after the first gate signals, means for receiving signals from the target, a capacitance, means for increasing the charge across the capacitance in accordance with the time of coincidence between the first gate signals and the received signals, means for decreasing the charge across the capacitance in accordance with the time of coincidence between the second gate signals and the received signals, a mass, a spring connected to the mass and to the missile to provide a relative displacement between the mass and the missile upon an acceleration of the missile, means associated with the missile and the mass for varying the charge across the capacitance in accordance with the relative displacement between the missile and the mass, and means operative in accordance with the charge across the capacitance to vary the times at which the first gate signals and second gate signals are produced.

11. In combination in a system for tracking a target for the interception of the target by a missile, a pair of oapacitances means for providing an initial balance of charge between the capacitances in accordance with a first determination of the distance between the target and the missile, means for providing an unbalance of the charges on the capacitance in accordance with the relative speed between the missile and the target, a mass, a spring connected to the mass and to the missile to provide a relative displacement between the mass and the missile upon an acceleration of the missile, magnetic means, including an armature and a plurality of windings, associated with the mass and the missile for producing an error signal in accordance with a relative displacement between the mass and the missile, and means 'for introducing the error signal to the capacitances to adjust the unbalance in the charges across the capacitances for the production of gating signals at approximately the instant signals from the target are received at the missile.

.12. In combination in a system for tracking a target for the interception of the target by a missile, means for i producing first gate signals, means for producing second 1 gate signals immediately after the first gate signals, means for receiving signals from the target, a capacitance, means for increasing the charge across the capacitance in accordance with the time of coincidence between the first gate signals and the received signals, means for decreasing the charge across the capacitance in accordance with the time of coincidence between the second gate signals and the received signals, a mass, a spring connected to the mass and to the missile to provide a relative displacement between the mass and the missile upon an acceleration of the missile, an armature, a pair of windings having balanced positions relative to the armature to produce a pair of equal voltages for a condition of substantially Mullah. m.i..mwmmwumwmllumn 3,231,888 9 10 no acceleration of the missile, the armature and wind- References Cited by the Examiner ings being associated with the missile and the mass to UNITED STATES PATENTS provide an unbalance in the disposition of the armature relative to the windings in accordance with any disy i" placement between the mass and the missile, and means 5 516356 7/1950 3 5 7 associated with the windings for varying the times at which the first and second gate signals are produced in ac- CHESTER L JUSTUS Primary Examiner cordance with any difierence in the voltages induced in the windings as a result of an unbalance in the position- NORMAN EVANS Exammering of the armature relative to the windings. 10 MICHAEL KARR, Assistant Examiner. 

1. IN COMBINATION IN A SYSTEM FOR TRACKING A TARGET FOR THE INTERCEPTION OF THE TARGET BY A MISSSILE, MEANS FOR PRODUCING A PAIR OF GATE SIGNALS, MEANS FOR RECEIVING A SIGNAL FROM THE TARGET, MEANS FOR PRODUCING AN ERROR SIGNAL HAVING AN AMPLITUDE DEPENDENT UPON THE COINCIDENCE BETWEEN EACH GATE SIGNAL AND RECEIVED SIGNAL TO PROVIDE AN INDICATION OF THE DISTANCE BETWEEN THE MISSILE AND THE TARGET AND THE VELOCITY OF THE MISSILE TOWARDS THE TARGET, MEANS FOR VARYING THE AMPLITUDE OF THE ERROR SIGNAL IN ACCORDANCE WITH THE ACCELERATION OF THE MISSILE, AND MEANS FOR VARYING THE TIME AT WHICH THE GATE SIGNAL ARE PRODUCED IN ACCORDANCE WITH THE AMPLITUDE OF THE ERROR SIGNAL. 